Equipment for processing flat articles, such as document sheets, cards, and the like, has long been known in which the articles to be processed are introduced one by one at the entrance to a transport path. Such equipment generally comprises endless belts or rotating drive rollers, for routing the articles to an exit of the transport path, moving successively via at least two systems arranged for processing the articles. The systems may be of the type described for example in French Pat. Nos. 1,379,259 and 2,078,087. In such systems it often happens that the two processing systems operate at different processing speeds, so that if the work done by the upstream processing system is done in a shorter time than that done by the other processing system, then an article driven continuously via the transport path may quite likely arrive at the entrance to this other system before the other system has finished processing the preceding article. In such case, it is absolutely necessary to provide a buffer system for temporary storage of articles such that the articles that have been processed by the faster upstream processing system accumulate and await the opportunity to be processed by the downstream processing system. Equipment for processing articles that includes a temporary buffer storage system disposed in between two processing systems is shown for example in French Patent No. 2,379,860.
Storage apparatus intended for temporary storage of articles have also been used in certain article sorting machines. One such known sorting machine has been described in the twenty-fifth supplement, No. 76,410, to French Patent No. 1,048,767. As disclosed in the patent, the articles to be sorted are introduced one by one at an arbitrary rate at the entrance to a transport path and are stored in an intermediate buffer store from which they are then removed so as to be sent at a uniform rate and speed to a receiving station that assures the sorting of the articles. The intermediate buffer store includes a wall against which the articles that are driven by the transport path abut as they arrive in the buffer store; hence this system appears to divide this transport path into two sections or feed tracks. Accordingly, the articles to be sorted, which are introduced at the entrance to a first feed track, are routed via this track and introduced into the buffer storage, where they are then stopped by the wall as they abut it. The articles that are immobilized in this buffer storage are then removed from it one by one in the opposite direction from that in which they were fed into the system, and are then engaged at the entrance to a second feed track, which routes them to the receiving station that is intended to perform the sorting. Storage apparatus of this generic type may naturally be used in the aforementioned article processing equipment that includes at least two article processing systems, as well as in equipment that includes only a single processing system but in which the transport path is arranged to allow an article to pass twice through this single processing system. Thus a sheet printing machine is known, for example, as described in the European Patent published as No. 0029647, in which each sheet, after having passed underneath the printing mechanism once so as to be printed on one of its two sides, is oriented toward a first feed track, which transports it to an intermediate storage magazine where the sheet is then stored. A removal mechanism allows this sheet to be removed subsequently from this magazine in the direction opposite that in which it was introduced, and to be engaged in a second feed track, which moves the sheet underneath the printing device. This sheet is then printed on its other side, and after its second passage underneath the printing mechanism it is finally routed toward a receiving box.
It is often indispensable for the article that has momentarily been stored in the storage magazine and is then removed from this magazine to be routed to the processing system located immediately downstream so as to arrive beneath this second system at a precise predetermined instant. This condition cannot be met unless the removal device with which the storage system is equipped can assure that the articles contained in the storage magazine will be removed from it without any variation from one article to the other in terms of the time required to effect this removal. Furthermore, in some applications, the storage magazine must be designed so as to assure the storage of more than one article at a time, while allowing the articles so stored to be subsequently removed one at a time.
The storage apparatus additionally described in the aforementioned supplement No. 76.410 and in the aforementioned European Patent No. 0029647 meet the second of the above two conditions, but not the first. The removal device with which they are equipped includes only one endless belt, which has a coefficient of friction too low to assure that the articles placed in contact with it will be driven without sliding. Thus it may happen that these articles are removed from storage with a certain delay, which varies from one article to another, or even that they are not removed at all. In a variant embodiment described in the aforementioned supplement No. 76.410, this disadvantage does not arise because of the fact that the removal device comprises a pneumatic suction device. Nevertheless, this suction device does not provide as much satisfaction as desired, because in order for the articles to be driven properly, the negative pressure value has to be adjusted as a function of the mass and rigidity of the articles, which makes this adjustment particularly delicate.
Another form of storage apparatus has been additionally described in U.S. Pat. No. 3,416,791. This arrangement includes a pocket in which each article is momentarily stored and a removal mechanism, which comprises, first, a friction roller driven in rotation and passing across a window made in one of the internal partitions of this pocket so as to come into contact with an article stored inside it and, second, a pressure roller integrally connected to an actuating device. Normally this pressure roller is spaced apart from the friction roller, but when the actuating device is excited it is capable of being urged toward the friction roller to allow an article stored in the pocket to be constrained between the friction roller and the pressure roller and thus to be removed from the pocket.
This latter arrangement does meet the first of the two conditions given above, but it does not meet the second condition at all, because if two articles are stored in the pocket at the same time it would then be impossible for these two articles to be removed from the pocket one at a time.